On Sunday, April 10, 2022 at 6:28:18 AM UTC-7, Eric Greenwell wrote:
> On 4/9/2022 11:49 PM, 2G wrote:
> > On Friday, April 8, 2022 at 6:43:29 AM UTC-7, Eric Greenwell wrote:
> >> On 4/7/2022 9:49 PM, 2G wrote:
> >>> On Wednesday, April 6, 2022 at 8:38:18 PM UTC-7, Eric Greenwell wrote:
> >> ...
> >>>> I was speaking specifically about the Taurus situation. After that accident, there were
> >>>> major changes in design and manufacturing, and EASA regulations, that likely make pouch
> >>>> and cylindrical systems much closer in safety.
> >>>>
> >>>> A major fire anywhere on an aircraft is a very serious situation! Obviously, the
> >>>> manufacturers know this, and design the battery pack and it's installation reduce the
> >>>> risk. For example, the wing roots are sealed to prevent fumes from entering the fuselage,
> >>>> and venting is used to discharge the fumes from the wing. This shows a fume vent on the
> >>>> Antares:
> >>>>
> >>>> https://nordicgliding-com.translate.goog/opdateret-lange-antares-faar-tesla-batterier/?_x_tr_sl=da&_x_tr_tl=en&_x_tr_hl=en-US&_x_tr_pto=nui
> >>>>
> >>>> Scroll down about half way to "Great demands on security".
> >>>>
> >>>> Vibration and G loads while operating a glider isn't a problem for the cylindrical cells,
> >>>> as they are very sturdy. Look up the specs for a typical 16850 cell, such as the
> >>>> Sony/Murata VCT6 cells used in the Jeta.
> >>>
> >>> This is a statement devoid of evidence. I, on the other hand, presented PLENTY of evidence to the contrary.
> >>>
> >>> Tom
> >> 18650 cells are used by the military, NASA rockets them into space, and EASA and others
> >> allow their use in aircraft. So please, take the time to look up the physical specs
> >> (vibration, etc) on the VCT6 cells, or pretty much any 18650 cell of the same chemistry.
> >> Those are the ones used in gliders. Once you have those specs, you can compare the specs
> >> to the loads those batteries experience in glider use. That's the evidence you need to
> >> show us if you want to persuade anyone a glider is a "rough ride"!
> >> --
> >> Eric Greenwell - USA
> >> - "A Guide to Self-launching Sailplane Operation"
> >> https://sites.google.com/site/motorgliders/publications
> >
> > Eric,
> >
> > I would if I could - the manufacturers don't provide any specs on vibration or shock that I have seen, indicating that they don't test for this. NASA doesn't use large quantities of batteries, so they won't provide any useful information. EASA also certified the problematic Taurus Electro. This falls into the category of absence of proof is not proof of absence. The ONLY proof I recognize are actual fires.
> >
> > Tom
> The certification standards have changed substantially because of the Taurus fire, and as
> I have pointed out before, it was a very different design than what Schleicher is
> producing. You have offered no evidence, much less proof, that the "actual fires" resulted
> from vibration or G loading. And, if NASA's experience doesn't provide useful information
> because their battery packs are smaller than glider pack, then I will continue to claim
> car fires or utility fires also do not provide useful information, since they use ten
> times to thousands of times as many batteries.
> --
> Eric Greenwell - USA
> - "A Guide to Self-launching Sailplane Operation"
> https://sites.google.com/site/motorgliders/publications

I have done nothing BUT provide "proof" of shock and vibration induced battery thermal runaways (also called "fires"). You may not accept this, but FES knows it to be a problem of such magnitude that they have put shock sensors on their battery packs. An excellent summary of the issues is presented in "Evaluation of Batteries for Safe Air Transport" (https://www.mdpi.com/1996-1073/9/5/340), which references 27 other studies. Note that this was published six years ago, so I can assume that much more research has been done. Then, there is the McMicken battery farm fire which exposed systemic defects in the manufacture of lithium cells used in the farm (which has been extensively discussed on RAS).

Tom

On Sunday, April 10, 2022 at 9:49:45 AM UTC-7, Arne Martin Güettler wrote:
> On Sunday, 10 April 2022 at 08:49:44 UTC+2, 2G wrote:
> > EASA also certified the problematic Taurus Electro. This falls into the category of absence of proof is not proof of absence. The ONLY proof I recognize are actual fires.
> No, the Taurus (electro or otherwise) is not EASA certified. The ones flying in Europe are registered as ultra light (which don't follow EASA rules) or experimental.

Ok, this seems to be the case, but the Electro has been certified by some countries:
https://www.pipistrel-aircraft.com/aircraft/electric-flight/taurus-electro/#tab-id-4
And the Electro was designed by aeronautical and electrical engineers, and manufactured by a respected aviation company, Pipistrel. This demonstrates that an aircraft's pedigree, by itself, is no guarantee of safety. The Boeing 787 was, and is, certified by the FAA, but had a notorious lithium battery fire after being certified:
https://www.reuters.com/article/us-boeing-787-battery/design-flaws-led-to-2013-lithium-ion-battery-fire-in-boeing-787-u-s-ntsb-idUSKCN0JF35G20141202

Tom

On 4/10/2022 9:49 AM, 2G wrote:
> On Sunday, April 10, 2022 at 6:28:18 AM UTC-7, Eric Greenwell wrote:
>> On 4/9/2022 11:49 PM, 2G wrote:
>>> On Friday, April 8, 2022 at 6:43:29 AM UTC-7, Eric Greenwell wrote:
>>>> On 4/7/2022 9:49 PM, 2G wrote:
>>>>> On Wednesday, April 6, 2022 at 8:38:18 PM UTC-7, Eric Greenwell wrote:
>>>> ...
>>>>>> I was speaking specifically about the Taurus situation. After that accident, there were
>>>>>> major changes in design and manufacturing, and EASA regulations, that likely make pouch
>>>>>> and cylindrical systems much closer in safety.
>>>>>>
>>>>>> A major fire anywhere on an aircraft is a very serious situation! Obviously, the
>>>>>> manufacturers know this, and design the battery pack and it's installation reduce the
>>>>>> risk. For example, the wing roots are sealed to prevent fumes from entering the fuselage,
>>>>>> and venting is used to discharge the fumes from the wing. This shows a fume vent on the
>>>>>> Antares:
>>>>>>
>>>>>> https://nordicgliding-com.translate.goog/opdateret-lange-antares-faar-tesla-batterier/?_x_tr_sl=da&_x_tr_tl=en&_x_tr_hl=en-US&_x_tr_pto=nui
>>>>>>
>>>>>> Scroll down about half way to "Great demands on security".
>>>>>>
>>>>>> Vibration and G loads while operating a glider isn't a problem for the cylindrical cells,
>>>>>> as they are very sturdy. Look up the specs for a typical 16850 cell, such as the
>>>>>> Sony/Murata VCT6 cells used in the Jeta.
>>>>>
>>>>> This is a statement devoid of evidence. I, on the other hand, presented PLENTY of evidence to the contrary.
>>>>>
>>>>> Tom
>>>> 18650 cells are used by the military, NASA rockets them into space, and EASA and others
>>>> allow their use in aircraft. So please, take the time to look up the physical specs
>>>> (vibration, etc) on the VCT6 cells, or pretty much any 18650 cell of the same chemistry.
>>>> Those are the ones used in gliders. Once you have those specs, you can compare the specs
>>>> to the loads those batteries experience in glider use. That's the evidence you need to
>>>> show us if you want to persuade anyone a glider is a "rough ride"!
>>>> --
>>>> Eric Greenwell - USA
>>>> - "A Guide to Self-launching Sailplane Operation"
>>>> https://sites.google.com/site/motorgliders/publications
>>>
>>> Eric,
>>>
>>> I would if I could - the manufacturers don't provide any specs on vibration or shock that I have seen, indicating that they don't test for this. NASA doesn't use large quantities of batteries, so they won't provide any useful information. EASA also certified the problematic Taurus Electro. This falls into the category of absence of proof is not proof of absence. The ONLY proof I recognize are actual fires.
>>>
>>> Tom
>> The certification standards have changed substantially because of the Taurus fire, and as
>> I have pointed out before, it was a very different design than what Schleicher is
>> producing. You have offered no evidence, much less proof, that the "actual fires" resulted
>> from vibration or G loading. And, if NASA's experience doesn't provide useful information
>> because their battery packs are smaller than glider pack, then I will continue to claim
>> car fires or utility fires also do not provide useful information, since they use ten
>> times to thousands of times as many batteries.
>> --
>> Eric Greenwell - USA
>> - "A Guide to Self-launching Sailplane Operation"
>> https://sites.google.com/site/motorgliders/publications
>
> I have done nothing BUT provide "proof" of shock and vibration induced battery thermal runaways (also called "fires"). You may not accept this, but FES knows it to be a problem of such magnitude that they have put shock sensors on their battery packs. An excellent summary of the issues is presented in "Evaluation of Batteries for Safe Air Transport" (https://www.mdpi.com/1996-1073/9/5/340), which references 27 other studies. Note that this was published six years ago, so I can assume that much more research has been done. Then, there is the McMicken battery farm fire which exposed systemic defects in the manufacture of lithium cells used in the farm (which has been extensively discussed on RAS).
>
> Tom

The FES batteries are routinely removed for charging, and can be damaged by dropping them.
After the fires, the FES company realized pilots do not always report those incidents, and
do not always have the batteries examined after dropping them. The shock sensors are for
that reason, not for loads encountered in-flight.

My experience is gliders operate with very little vibration, and that's when flying from
rough grass fields. The total duration of the vibration per flight is less than a minute
(takeoff plus landing), and most motorgliders operate from smooth runways.

No one expects the cells to be perfect, which is why the EASA certification requires a
glider to safely endure a catastrophic cell failure.

--
Eric Greenwell - USA
- "A Guide to Self-launching Sailplane Operation"
https://sites.google.com/site/motorgliders/publications

On Sunday, April 10, 2022 at 1:45:43 PM UTC-4, Eric Greenwell wrote:
> On 4/10/2022 9:49 AM, 2G wrote:
> > On Sunday, April 10, 2022 at 6:28:18 AM UTC-7, Eric Greenwell wrote:
> >> On 4/9/2022 11:49 PM, 2G wrote:
> >>> On Friday, April 8, 2022 at 6:43:29 AM UTC-7, Eric Greenwell wrote:
> >>>> On 4/7/2022 9:49 PM, 2G wrote:
> >>>>> On Wednesday, April 6, 2022 at 8:38:18 PM UTC-7, Eric Greenwell wrote:
> >>>> ...
> >>>>>> I was speaking specifically about the Taurus situation. After that accident, there were
> >>>>>> major changes in design and manufacturing, and EASA regulations, that likely make pouch
> >>>>>> and cylindrical systems much closer in safety.
> >>>>>>
> >>>>>> A major fire anywhere on an aircraft is a very serious situation! Obviously, the
> >>>>>> manufacturers know this, and design the battery pack and it's installation reduce the
> >>>>>> risk. For example, the wing roots are sealed to prevent fumes from entering the fuselage,
> >>>>>> and venting is used to discharge the fumes from the wing. This shows a fume vent on the
> >>>>>> Antares:
> >>>>>>
> >>>>>> https://nordicgliding-com.translate.goog/opdateret-lange-antares-faar-tesla-batterier/?_x_tr_sl=da&_x_tr_tl=en&_x_tr_hl=en-US&_x_tr_pto=nui
> >>>>>>
> >>>>>> Scroll down about half way to "Great demands on security".
> >>>>>>
> >>>>>> Vibration and G loads while operating a glider isn't a problem for the cylindrical cells,
> >>>>>> as they are very sturdy. Look up the specs for a typical 16850 cell, such as the
> >>>>>> Sony/Murata VCT6 cells used in the Jeta.
> >>>>>
> >>>>> This is a statement devoid of evidence. I, on the other hand, presented PLENTY of evidence to the contrary.
> >>>>>
> >>>>> Tom
> >>>> 18650 cells are used by the military, NASA rockets them into space, and EASA and others
> >>>> allow their use in aircraft. So please, take the time to look up the physical specs
> >>>> (vibration, etc) on the VCT6 cells, or pretty much any 18650 cell of the same chemistry.
> >>>> Those are the ones used in gliders. Once you have those specs, you can compare the specs
> >>>> to the loads those batteries experience in glider use. That's the evidence you need to
> >>>> show us if you want to persuade anyone a glider is a "rough ride"!
> >>>> --
> >>>> Eric Greenwell - USA
> >>>> - "A Guide to Self-launching Sailplane Operation"
> >>>> https://sites.google.com/site/motorgliders/publications
> >>>
> >>> Eric,
> >>>
> >>> I would if I could - the manufacturers don't provide any specs on vibration or shock that I have seen, indicating that they don't test for this. NASA doesn't use large quantities of batteries, so they won't provide any useful information. EASA also certified the problematic Taurus Electro. This falls into the category of absence of proof is not proof of absence. The ONLY proof I recognize are actual fires.
> >>>
> >>> Tom
> >> The certification standards have changed substantially because of the Taurus fire, and as
> >> I have pointed out before, it was a very different design than what Schleicher is
> >> producing. You have offered no evidence, much less proof, that the "actual fires" resulted
> >> from vibration or G loading. And, if NASA's experience doesn't provide useful information
> >> because their battery packs are smaller than glider pack, then I will continue to claim
> >> car fires or utility fires also do not provide useful information, since they use ten
> >> times to thousands of times as many batteries.
> >> --
> >> Eric Greenwell - USA
> >> - "A Guide to Self-launching Sailplane Operation"
> >> https://sites.google.com/site/motorgliders/publications
> >
> > I have done nothing BUT provide "proof" of shock and vibration induced battery thermal runaways (also called "fires"). You may not accept this, but FES knows it to be a problem of such magnitude that they have put shock sensors on their battery packs. An excellent summary of the issues is presented in "Evaluation of Batteries for Safe Air Transport" (https://www.mdpi.com/1996-1073/9/5/340), which references 27 other studies. Note that this was published six years ago, so I can assume that much more research has been done. Then, there is the McMicken battery farm fire which exposed systemic defects in the manufacture of lithium cells used in the farm (which has been extensively discussed on RAS).
> >
> > Tom
> The FES batteries are routinely removed for charging, and can be damaged by dropping them.
> After the fires, the FES company realized pilots do not always report those incidents, and
> do not always have the batteries examined after dropping them. The shock sensors are for
> that reason, not for loads encountered in-flight.
>
> My experience is gliders operate with very little vibration, and that's when flying from
> rough grass fields. The total duration of the vibration per flight is less than a minute
> (takeoff plus landing), and most motorgliders operate from smooth runways..
>
> No one expects the cells to be perfect, which is why the EASA certification requires a
> glider to safely endure a catastrophic cell failure.
> --
> Eric Greenwell - USA
> - "A Guide to Self-launching Sailplane Operation"
> https://sites.google.com/site/motorgliders/publications

The FES gliders use "pouch" cells that provide higher stored energy per pound than 18650 type cells. The down side is that they are much more easily damaged as demonstrated by the fires that occurred. Contributing was a potentially conductive battery box. Additionally small metal shards resulting from the assembly process are thought to have contributed to possible cell damage. Once these cells go there isn't much to stop them. Containment is the only real option. The FES people have re done the enclosure, modified assembly, and added monitoring. Since that time I am not aware of any more fires.
That said I have chosen to use the 18650 style cells that have been demonstrated to tolerate a single catastrophic damage(the nail test) without damaging adjacent cells. The way they are supported in the assembly leaves no room for movement so I expect no issues with shock or vibration.
FWIW
UH

On Sunday, April 10, 2022 at 10:45:43 AM UTC-7, Eric Greenwell wrote:
> On 4/10/2022 9:49 AM, 2G wrote:
> > On Sunday, April 10, 2022 at 6:28:18 AM UTC-7, Eric Greenwell wrote:
> >> On 4/9/2022 11:49 PM, 2G wrote:
> >>> On Friday, April 8, 2022 at 6:43:29 AM UTC-7, Eric Greenwell wrote:
> >>>> On 4/7/2022 9:49 PM, 2G wrote:
> >>>>> On Wednesday, April 6, 2022 at 8:38:18 PM UTC-7, Eric Greenwell wrote:
> >>>> ...
> >>>>>> I was speaking specifically about the Taurus situation. After that accident, there were
> >>>>>> major changes in design and manufacturing, and EASA regulations, that likely make pouch
> >>>>>> and cylindrical systems much closer in safety.
> >>>>>>
> >>>>>> A major fire anywhere on an aircraft is a very serious situation! Obviously, the
> >>>>>> manufacturers know this, and design the battery pack and it's installation reduce the
> >>>>>> risk. For example, the wing roots are sealed to prevent fumes from entering the fuselage,
> >>>>>> and venting is used to discharge the fumes from the wing. This shows a fume vent on the
> >>>>>> Antares:
> >>>>>>
> >>>>>> https://nordicgliding-com.translate.goog/opdateret-lange-antares-faar-tesla-batterier/?_x_tr_sl=da&_x_tr_tl=en&_x_tr_hl=en-US&_x_tr_pto=nui
> >>>>>>
> >>>>>> Scroll down about half way to "Great demands on security".
> >>>>>>
> >>>>>> Vibration and G loads while operating a glider isn't a problem for the cylindrical cells,
> >>>>>> as they are very sturdy. Look up the specs for a typical 16850 cell, such as the
> >>>>>> Sony/Murata VCT6 cells used in the Jeta.
> >>>>>
> >>>>> This is a statement devoid of evidence. I, on the other hand, presented PLENTY of evidence to the contrary.
> >>>>>
> >>>>> Tom
> >>>> 18650 cells are used by the military, NASA rockets them into space, and EASA and others
> >>>> allow their use in aircraft. So please, take the time to look up the physical specs
> >>>> (vibration, etc) on the VCT6 cells, or pretty much any 18650 cell of the same chemistry.
> >>>> Those are the ones used in gliders. Once you have those specs, you can compare the specs
> >>>> to the loads those batteries experience in glider use. That's the evidence you need to
> >>>> show us if you want to persuade anyone a glider is a "rough ride"!
> >>>> --
> >>>> Eric Greenwell - USA
> >>>> - "A Guide to Self-launching Sailplane Operation"
> >>>> https://sites.google.com/site/motorgliders/publications
> >>>
> >>> Eric,
> >>>
> >>> I would if I could - the manufacturers don't provide any specs on vibration or shock that I have seen, indicating that they don't test for this. NASA doesn't use large quantities of batteries, so they won't provide any useful information. EASA also certified the problematic Taurus Electro. This falls into the category of absence of proof is not proof of absence. The ONLY proof I recognize are actual fires.
> >>>
> >>> Tom
> >> The certification standards have changed substantially because of the Taurus fire, and as
> >> I have pointed out before, it was a very different design than what Schleicher is
> >> producing. You have offered no evidence, much less proof, that the "actual fires" resulted
> >> from vibration or G loading. And, if NASA's experience doesn't provide useful information
> >> because their battery packs are smaller than glider pack, then I will continue to claim
> >> car fires or utility fires also do not provide useful information, since they use ten
> >> times to thousands of times as many batteries.
> >> --
> >> Eric Greenwell - USA
> >> - "A Guide to Self-launching Sailplane Operation"
> >> https://sites.google.com/site/motorgliders/publications
> >
> > I have done nothing BUT provide "proof" of shock and vibration induced battery thermal runaways (also called "fires"). You may not accept this, but FES knows it to be a problem of such magnitude that they have put shock sensors on their battery packs. An excellent summary of the issues is presented in "Evaluation of Batteries for Safe Air Transport" (https://www.mdpi.com/1996-1073/9/5/340), which references 27 other studies. Note that this was published six years ago, so I can assume that much more research has been done. Then, there is the McMicken battery farm fire which exposed systemic defects in the manufacture of lithium cells used in the farm (which has been extensively discussed on RAS).
> >
> > Tom
> The FES batteries are routinely removed for charging, and can be damaged by dropping them.
> After the fires, the FES company realized pilots do not always report those incidents, and
> do not always have the batteries examined after dropping them. The shock sensors are for
> that reason, not for loads encountered in-flight.
>
> My experience is gliders operate with very little vibration, and that's when flying from
> rough grass fields. The total duration of the vibration per flight is less than a minute
> (takeoff plus landing), and most motorgliders operate from smooth runways..
>
> No one expects the cells to be perfect, which is why the EASA certification requires a
> glider to safely endure a catastrophic cell failure.
> --
> Eric Greenwell - USA
> - "A Guide to Self-launching Sailplane Operation"
> https://sites.google.com/site/motorgliders/publications

To state there is little to no vibration in flight just isn't believable. Certainly, there is in any turbulent flight. Just entering and exiting a thermal is turbulent. Plus, the glider is exposed to substantial vibration during trailering and ground operations. And lithium battery thermal runaways have occurred in a vibration-free environment (i.e. battery farm fires). Plus, the batteries are being exposed to extreme altitude fluctuations, which subject them to atmospheric pressure stresses. While we still don't know the cause of the Felicity Ace fire, there were rough seas prior to its start..

Tom

On 4/10/2022 6:22 PM, 2G wrote:

>> The FES batteries are routinely removed for charging, and can be damaged by dropping them.
>> After the fires, the FES company realized pilots do not always report those incidents, and
>> do not always have the batteries examined after dropping them. The shock sensors are for
>> that reason, not for loads encountered in-flight.
>>
>> My experience is gliders operate with very little vibration, and that's when flying from
>> rough grass fields. The total duration of the vibration per flight is less than a minute
>> (takeoff plus landing), and most motorgliders operate from smooth runways.
>>
>> No one expects the cells to be perfect, which is why the EASA certification requires a
>> glider to safely endure a catastrophic cell failure.
>> --
>> Eric Greenwell - USA
>> - "A Guide to Self-launching Sailplane Operation"
>> https://sites.google.com/site/motorgliders/publications
>
> To state there is little to no vibration in flight just isn't believable. Certainly, there is in any turbulent flight. Just entering and exiting a thermal is turbulent. Plus, the glider is exposed to substantial vibration during trailering and ground operations. And lithium battery thermal runaways have occurred in a vibration-free environment (i.e. battery farm fires). Plus, the batteries are being exposed to extreme altitude fluctuations, which subject them to atmospheric pressure stresses. While we still don't know the cause of the Felicity Ace fire, there were rough seas prior to its start.
>
> Tom
I haven't heard anyone speak of vibration while a glider is flying, unless the motor was
running. To clarify what I mean by vibration, I'll use an automobile analogy: vibration is
what you feel when driving on a washboarded road. Turbulence in glider is felt as G
loading, not vibration. In cars, an analog to glider turbulence is speed bumps and strong
wind gusts.

I do agree that trailering effects on batteries in the glider are likely similar to what
cars experience with their batteries. I skimmed three studies on "vibration testing" 18650
cells used in cars; typically, they found some degradation in electrical performance and
some mechanical damage (observable with CAT scanning or similar), but made no mention of
fires. The strength, duration, the directions of test accelerations, and the chemistries
tested varied considerably between the studies I looked at.

I have not seen anything about altitude pressure issues for 18650 cells, and I don't
expect an 8 psi ambient pressure reduction (sea level to FL180) to affect a 16850 cell
that can withstand much higher internal pressures. The effects I did read about are
reduced cooling due to thinner air, and reduced capacity due to lower temperatures.

--
Eric Greenwell - USA
- "A Guide to Self-launching Sailplane Operation"
https://sites.google.com/site/motorgliders/publications

On Monday, April 11, 2022 at 11:11:06 AM UTC-7, Eric Greenwell wrote:
> On 4/10/2022 6:22 PM, 2G wrote:
>
> >> The FES batteries are routinely removed for charging, and can be damaged by dropping them.
> >> After the fires, the FES company realized pilots do not always report those incidents, and
> >> do not always have the batteries examined after dropping them. The shock sensors are for
> >> that reason, not for loads encountered in-flight.
> >>
> >> My experience is gliders operate with very little vibration, and that's when flying from
> >> rough grass fields. The total duration of the vibration per flight is less than a minute
> >> (takeoff plus landing), and most motorgliders operate from smooth runways.
> >>
> >> No one expects the cells to be perfect, which is why the EASA certification requires a
> >> glider to safely endure a catastrophic cell failure.
> >> --
> >> Eric Greenwell - USA
> >> - "A Guide to Self-launching Sailplane Operation"
> >> https://sites.google.com/site/motorgliders/publications
> >
> > To state there is little to no vibration in flight just isn't believable. Certainly, there is in any turbulent flight. Just entering and exiting a thermal is turbulent. Plus, the glider is exposed to substantial vibration during trailering and ground operations. And lithium battery thermal runaways have occurred in a vibration-free environment (i.e. battery farm fires).. Plus, the batteries are being exposed to extreme altitude fluctuations, which subject them to atmospheric pressure stresses. While we still don't know the cause of the Felicity Ace fire, there were rough seas prior to its start.
> >
> > Tom
> I haven't heard anyone speak of vibration while a glider is flying, unless the motor was
> running. To clarify what I mean by vibration, I'll use an automobile analogy: vibration is
> what you feel when driving on a washboarded road. Turbulence in glider is felt as G
> loading, not vibration. In cars, an analog to glider turbulence is speed bumps and strong
> wind gusts.
>
> I do agree that trailering effects on batteries in the glider are likely similar to what
> cars experience with their batteries. I skimmed three studies on "vibration testing" 18650
> cells used in cars; typically, they found some degradation in electrical performance and
> some mechanical damage (observable with CAT scanning or similar), but made no mention of
> fires. The strength, duration, the directions of test accelerations, and the chemistries
> tested varied considerably between the studies I looked at.
>
> I have not seen anything about altitude pressure issues for 18650 cells, and I don't
> expect an 8 psi ambient pressure reduction (sea level to FL180) to affect a 16850 cell
> that can withstand much higher internal pressures. The effects I did read about are
> reduced cooling due to thinner air, and reduced capacity due to lower temperatures.
> --
> Eric Greenwell - USA
> - "A Guide to Self-launching Sailplane Operation"
> https://sites.google.com/site/motorgliders/publications

Eric,

Flight safety is similar to guarding the President: the Secret Service has to be right 100% of the time, an assassin only has to be right once. If we decide some factor is irrelevant and are wrong, then accidents can occur. The 737Max comes to mind.

Did you read "Evaluation of Batteries for Safe Air Transport" (https://www.mdpi.com/1996-1073/9/5/340)? Section 4.2, Thermal and Mechanical Stress Testing, covers altitude pressure tests for batteries to be shipped by air. The situation is that if the battery case is sealed at sea level, and there is any air inside, it can create stress on the case when exposed to high altitudes. A manufacturer not listing a spec doesn't mean that spec is irrelevant ("absence of proof is not proof of absence").

I can't understand why electric glider batteries shouldn't be subjected to the same tests required for shipment by air transport. Note that these regulations were developed following several major air disasters involving lithium batteries:
*Asiana Airlines 747 near South Korea in July 2011 https://en.wikipedia.org/wiki/Asiana_Airlines_Flight_991#:~:text=On%2028%20July%202011%2C%20Asiana,people%20on%20board%2C%20were%20killed
*UPS 747 in Dubai
https://en.wikipedia.org/wiki/UPS_Airlines_Flight_6#:~:text=On%20September%203%2C%202010%2C%20the,air%20crash%20for%20UPS%20Airlines
*UPS DC-8 in Philadelphia, PA in February 2006
https://skybrary.aero/accidents-and-incidents/dc87-philadelphia-usa-2006#:~:text=On%207%20February%202006%2C%20a,the%20emergency%20services%20were%20alerted

I recommend that auto and aircraft manufacturers using electrical propulsion include high frequency transient recording instrumentation to detect microfaults occurring internal to the battery pack. I have personally measured high frequency noise being emitted by a failed lead-acid battery that was not there on a new battery. Any shorting in an individual cell will produce detectable current spikes that can be measured and recorded.

Personally, I think they will find that the Felicity Ace ship fire was caused by a lithium battery fire (if the cause can be isolated).

Tom

On 4/11/2022 2:57 PM, 2G wrote:
> On Monday, April 11, 2022 at 11:11:06 AM UTC-7, Eric Greenwell wrote:
>> On 4/10/2022 6:22 PM, 2G wrote:
....
>>>
>>> To state there is little to no vibration in flight just isn't believable. Certainly, there is in any turbulent flight. Just entering and exiting a thermal is turbulent. Plus, the glider is exposed to substantial vibration during trailering and ground operations. And lithium battery thermal runaways have occurred in a vibration-free environment (i.e. battery farm fires). Plus, the batteries are being exposed to extreme altitude fluctuations, which subject them to atmospheric pressure stresses. While we still don't know the cause of the Felicity Ace fire, there were rough seas prior to its start.
>>>
>>> Tom
>> I haven't heard anyone speak of vibration while a glider is flying, unless the motor was
>> running. To clarify what I mean by vibration, I'll use an automobile analogy: vibration is
>> what you feel when driving on a washboarded road. Turbulence in glider is felt as G
>> loading, not vibration. In cars, an analog to glider turbulence is speed bumps and strong
>> wind gusts.
>>
>> I do agree that trailering effects on batteries in the glider are likely similar to what
>> cars experience with their batteries. I skimmed three studies on "vibration testing" 18650
>> cells used in cars; typically, they found some degradation in electrical performance and
>> some mechanical damage (observable with CAT scanning or similar), but made no mention of
>> fires. The strength, duration, the directions of test accelerations, and the chemistries
>> tested varied considerably between the studies I looked at.
>>
>> I have not seen anything about altitude pressure issues for 18650 cells, and I don't
>> expect an 8 psi ambient pressure reduction (sea level to FL180) to affect a 16850 cell
>> that can withstand much higher internal pressures. The effects I did read about are
>> reduced cooling due to thinner air, and reduced capacity due to lower temperatures.
>> --
>> Eric Greenwell - USA
>> - "A Guide to Self-launching Sailplane Operation"
>> https://sites.google.com/site/motorgliders/publications
>
> Eric,
>
> Flight safety is similar to guarding the President: the Secret Service has to be right 100% of the time, an assassin only has to be right once. If we decide some factor is irrelevant and are wrong, then accidents can occur. The 737Max comes to mind.
>
> Did you read "Evaluation of Batteries for Safe Air Transport" (https://www.mdpi.com/1996-1073/9/5/340)? Section 4.2, Thermal and Mechanical Stress Testing, covers altitude pressure tests for batteries to be shipped by air. The situation is that if the battery case is sealed at sea level, and there is any air inside, it can create stress on the case when exposed to high altitudes. A manufacturer not listing a spec doesn't mean that spec is irrelevant ("absence of proof is not proof of absence").
>
> I can't understand why electric glider batteries shouldn't be subjected to the same tests required for shipment by air transport. Note that these regulations were developed following several major air disasters involving lithium batteries:
>
I did not read about air transport regulations, because gliders are not transporting
batteries, and the regulations for commercial carriage are hugely different EASA
regulations for gliders. The altitude tests you refer to are for the case, not for the
batteries.

Seriously, Tom: fires in cars, fires in utility scale power banks, fires in ships carrying
thousands of cars, regulations for shipping batteries in commercial aircraft? These are
very tenuously related to what Schleicher, et al, are trying to do. They must follow the
regulations for our aircraft, and not for these other uses. Please spend most of your
effort on systems for gliders, their regulations, and how they are working out for soaring
pilots, and we will be better informed about the gliders we want to fly.

--
Eric Greenwell - USA
- "A Guide to Self-launching Sailplane Operation"
https://sites.google.com/site/motorgliders/publications

On Monday, April 11, 2022 at 3:42:41 PM UTC-7, Eric Greenwell wrote:
> On 4/11/2022 2:57 PM, 2G wrote:
> > On Monday, April 11, 2022 at 11:11:06 AM UTC-7, Eric Greenwell wrote:
> >> On 4/10/2022 6:22 PM, 2G wrote:
> ...
> >>>
> >>> To state there is little to no vibration in flight just isn't believable. Certainly, there is in any turbulent flight. Just entering and exiting a thermal is turbulent. Plus, the glider is exposed to substantial vibration during trailering and ground operations. And lithium battery thermal runaways have occurred in a vibration-free environment (i.e. battery farm fires). Plus, the batteries are being exposed to extreme altitude fluctuations, which subject them to atmospheric pressure stresses. While we still don't know the cause of the Felicity Ace fire, there were rough seas prior to its start.
> >>>
> >>> Tom
> >> I haven't heard anyone speak of vibration while a glider is flying, unless the motor was
> >> running. To clarify what I mean by vibration, I'll use an automobile analogy: vibration is
> >> what you feel when driving on a washboarded road. Turbulence in glider is felt as G
> >> loading, not vibration. In cars, an analog to glider turbulence is speed bumps and strong
> >> wind gusts.
> >>
> >> I do agree that trailering effects on batteries in the glider are likely similar to what
> >> cars experience with their batteries. I skimmed three studies on "vibration testing" 18650
> >> cells used in cars; typically, they found some degradation in electrical performance and
> >> some mechanical damage (observable with CAT scanning or similar), but made no mention of
> >> fires. The strength, duration, the directions of test accelerations, and the chemistries
> >> tested varied considerably between the studies I looked at.
> >>
> >> I have not seen anything about altitude pressure issues for 18650 cells, and I don't
> >> expect an 8 psi ambient pressure reduction (sea level to FL180) to affect a 16850 cell
> >> that can withstand much higher internal pressures. The effects I did read about are
> >> reduced cooling due to thinner air, and reduced capacity due to lower temperatures.
> >> --
> >> Eric Greenwell - USA
> >> - "A Guide to Self-launching Sailplane Operation"
> >> https://sites.google.com/site/motorgliders/publications
> >
> > Eric,
> >
> > Flight safety is similar to guarding the President: the Secret Service has to be right 100% of the time, an assassin only has to be right once. If we decide some factor is irrelevant and are wrong, then accidents can occur. The 737Max comes to mind.
> >
> > Did you read "Evaluation of Batteries for Safe Air Transport" (https://www.mdpi.com/1996-1073/9/5/340)? Section 4.2, Thermal and Mechanical Stress Testing, covers altitude pressure tests for batteries to be shipped by air.. The situation is that if the battery case is sealed at sea level, and there is any air inside, it can create stress on the case when exposed to high altitudes. A manufacturer not listing a spec doesn't mean that spec is irrelevant ("absence of proof is not proof of absence").
> >
> > I can't understand why electric glider batteries shouldn't be subjected to the same tests required for shipment by air transport. Note that these regulations were developed following several major air disasters involving lithium batteries:
> >
> I did not read about air transport regulations, because gliders are not transporting
> batteries, and the regulations for commercial carriage are hugely different EASA
> regulations for gliders. The altitude tests you refer to are for the case, not for the
> batteries.
>
> Seriously, Tom: fires in cars, fires in utility scale power banks, fires in ships carrying
> thousands of cars, regulations for shipping batteries in commercial aircraft? These are
> very tenuously related to what Schleicher, et al, are trying to do. They must follow the
> regulations for our aircraft, and not for these other uses. Please spend most of your
> effort on systems for gliders, their regulations, and how they are working out for soaring
> pilots, and we will be better informed about the gliders we want to fly.
> --
> Eric Greenwell - USA
> - "A Guide to Self-launching Sailplane Operation"
> https://sites.google.com/site/motorgliders/publications

WHY didn't read about those regulations? Do you think that what they are worried about concerning battery safety SOMEHOW doesn't apply to you?? A battery fire IS a battery fire whether it occurs on a 747 or on a GP-15.

The chemistry of the batteries involved on fires on ships, planes and cars are IDENTICAL to what you will be flying with in your GP-15. I am astounded by your denial of the very real safety risks concerning these batteries. I am, truly, at a loss for words...

Tom

On 4/11/2022 7:57 PM, 2G wrote:
> On Monday, April 11, 2022 at 3:42:41 PM UTC-7, Eric Greenwell wrote:
>> On 4/11/2022 2:57 PM, 2G wrote:
>>> On Monday, April 11, 2022 at 11:11:06 AM UTC-7, Eric Greenwell wrote:
>>>> On 4/10/2022 6:22 PM, 2G wrote:
>> ...
>>>>>
>>>>> To state there is little to no vibration in flight just isn't believable. Certainly, there is in any turbulent flight. Just entering and exiting a thermal is turbulent. Plus, the glider is exposed to substantial vibration during trailering and ground operations. And lithium battery thermal runaways have occurred in a vibration-free environment (i.e. battery farm fires). Plus, the batteries are being exposed to extreme altitude fluctuations, which subject them to atmospheric pressure stresses. While we still don't know the cause of the Felicity Ace fire, there were rough seas prior to its start.
>>>>>
>>>>> Tom
>>>> I haven't heard anyone speak of vibration while a glider is flying, unless the motor was
>>>> running. To clarify what I mean by vibration, I'll use an automobile analogy: vibration is
>>>> what you feel when driving on a washboarded road. Turbulence in glider is felt as G
>>>> loading, not vibration. In cars, an analog to glider turbulence is speed bumps and strong
>>>> wind gusts.
>>>>
>>>> I do agree that trailering effects on batteries in the glider are likely similar to what
>>>> cars experience with their batteries. I skimmed three studies on "vibration testing" 18650
>>>> cells used in cars; typically, they found some degradation in electrical performance and
>>>> some mechanical damage (observable with CAT scanning or similar), but made no mention of
>>>> fires. The strength, duration, the directions of test accelerations, and the chemistries
>>>> tested varied considerably between the studies I looked at.
>>>>
>>>> I have not seen anything about altitude pressure issues for 18650 cells, and I don't
>>>> expect an 8 psi ambient pressure reduction (sea level to FL180) to affect a 16850 cell
>>>> that can withstand much higher internal pressures. The effects I did read about are
>>>> reduced cooling due to thinner air, and reduced capacity due to lower temperatures.
>>>> --
>>>> Eric Greenwell - USA
>>>> - "A Guide to Self-launching Sailplane Operation"
>>>> https://sites.google.com/site/motorgliders/publications
>>>
>>> Eric,
>>>
>>> Flight safety is similar to guarding the President: the Secret Service has to be right 100% of the time, an assassin only has to be right once. If we decide some factor is irrelevant and are wrong, then accidents can occur. The 737Max comes to mind.
>>>
>>> Did you read "Evaluation of Batteries for Safe Air Transport" (https://www.mdpi.com/1996-1073/9/5/340)? Section 4.2, Thermal and Mechanical Stress Testing, covers altitude pressure tests for batteries to be shipped by air. The situation is that if the battery case is sealed at sea level, and there is any air inside, it can create stress on the case when exposed to high altitudes. A manufacturer not listing a spec doesn't mean that spec is irrelevant ("absence of proof is not proof of absence").
>>>
>>> I can't understand why electric glider batteries shouldn't be subjected to the same tests required for shipment by air transport. Note that these regulations were developed following several major air disasters involving lithium batteries:
>>>
>> I did not read about air transport regulations, because gliders are not transporting
>> batteries, and the regulations for commercial carriage are hugely different EASA
>> regulations for gliders. The altitude tests you refer to are for the case, not for the
>> batteries.
>>
>> Seriously, Tom: fires in cars, fires in utility scale power banks, fires in ships carrying
>> thousands of cars, regulations for shipping batteries in commercial aircraft? These are
>> very tenuously related to what Schleicher, et al, are trying to do. They must follow the
>> regulations for our aircraft, and not for these other uses. Please spend most of your
>> effort on systems for gliders, their regulations, and how they are working out for soaring
>> pilots, and we will be better informed about the gliders we want to fly.
>> --
>> Eric Greenwell - USA
>> - "A Guide to Self-launching Sailplane Operation"
>> https://sites.google.com/site/motorgliders/publications
>
> WHY didn't read about those regulations? Do you think that what they are worried about concerning battery safety SOMEHOW doesn't apply to you?? A battery fire IS a battery fire whether it occurs on a 747 or on a GP-15.
>
> The chemistry of the batteries involved on fires on ships, planes and cars are IDENTICAL to what you will be flying with in your GP-15. I am astounded by your denial of the very real safety risks concerning these batteries. I am, truly, at a loss for words...
>
> Tom
I think you should learn the certification requirements for gliders, learn what the glider
manufacturers are doing to meet these regulations, examine the problems electric gliders
have had, and discuss the issues with as many knowledgeable people as you can. Only then
will you have the knowledge needed to give us credible advice.

--
Eric Greenwell - USA
- "A Guide to Self-launching Sailplane Operation"
https://sites.google.com/site/motorgliders/publications

On Tuesday, April 12, 2022 at 7:35:34 AM UTC-7, Eric Greenwell wrote:
> On 4/11/2022 7:57 PM, 2G wrote:
> > On Monday, April 11, 2022 at 3:42:41 PM UTC-7, Eric Greenwell wrote:
> >> On 4/11/2022 2:57 PM, 2G wrote:
> >>> On Monday, April 11, 2022 at 11:11:06 AM UTC-7, Eric Greenwell wrote:
> >>>> On 4/10/2022 6:22 PM, 2G wrote:
> >> ...
> >>>>>
> >>>>> To state there is little to no vibration in flight just isn't believable. Certainly, there is in any turbulent flight. Just entering and exiting a thermal is turbulent. Plus, the glider is exposed to substantial vibration during trailering and ground operations. And lithium battery thermal runaways have occurred in a vibration-free environment (i.e. battery farm fires). Plus, the batteries are being exposed to extreme altitude fluctuations, which subject them to atmospheric pressure stresses. While we still don't know the cause of the Felicity Ace fire, there were rough seas prior to its start.
> >>>>>
> >>>>> Tom
> >>>> I haven't heard anyone speak of vibration while a glider is flying, unless the motor was
> >>>> running. To clarify what I mean by vibration, I'll use an automobile analogy: vibration is
> >>>> what you feel when driving on a washboarded road. Turbulence in glider is felt as G
> >>>> loading, not vibration. In cars, an analog to glider turbulence is speed bumps and strong
> >>>> wind gusts.
> >>>>
> >>>> I do agree that trailering effects on batteries in the glider are likely similar to what
> >>>> cars experience with their batteries. I skimmed three studies on "vibration testing" 18650
> >>>> cells used in cars; typically, they found some degradation in electrical performance and
> >>>> some mechanical damage (observable with CAT scanning or similar), but made no mention of
> >>>> fires. The strength, duration, the directions of test accelerations, and the chemistries
> >>>> tested varied considerably between the studies I looked at.
> >>>>
> >>>> I have not seen anything about altitude pressure issues for 18650 cells, and I don't
> >>>> expect an 8 psi ambient pressure reduction (sea level to FL180) to affect a 16850 cell
> >>>> that can withstand much higher internal pressures. The effects I did read about are
> >>>> reduced cooling due to thinner air, and reduced capacity due to lower temperatures.
> >>>> --
> >>>> Eric Greenwell - USA
> >>>> - "A Guide to Self-launching Sailplane Operation"
> >>>> https://sites.google.com/site/motorgliders/publications
> >>>
> >>> Eric,
> >>>
> >>> Flight safety is similar to guarding the President: the Secret Service has to be right 100% of the time, an assassin only has to be right once. If we decide some factor is irrelevant and are wrong, then accidents can occur. The 737Max comes to mind.
> >>>
> >>> Did you read "Evaluation of Batteries for Safe Air Transport" (https://www.mdpi.com/1996-1073/9/5/340)? Section 4.2, Thermal and Mechanical Stress Testing, covers altitude pressure tests for batteries to be shipped by air. The situation is that if the battery case is sealed at sea level, and there is any air inside, it can create stress on the case when exposed to high altitudes. A manufacturer not listing a spec doesn't mean that spec is irrelevant ("absence of proof is not proof of absence").
> >>>
> >>> I can't understand why electric glider batteries shouldn't be subjected to the same tests required for shipment by air transport. Note that these regulations were developed following several major air disasters involving lithium batteries:
> >>>
> >> I did not read about air transport regulations, because gliders are not transporting
> >> batteries, and the regulations for commercial carriage are hugely different EASA
> >> regulations for gliders. The altitude tests you refer to are for the case, not for the
> >> batteries.
> >>
> >> Seriously, Tom: fires in cars, fires in utility scale power banks, fires in ships carrying
> >> thousands of cars, regulations for shipping batteries in commercial aircraft? These are
> >> very tenuously related to what Schleicher, et al, are trying to do. They must follow the
> >> regulations for our aircraft, and not for these other uses. Please spend most of your
> >> effort on systems for gliders, their regulations, and how they are working out for soaring
> >> pilots, and we will be better informed about the gliders we want to fly.
> >> --
> >> Eric Greenwell - USA
> >> - "A Guide to Self-launching Sailplane Operation"
> >> https://sites.google.com/site/motorgliders/publications
> >
> > WHY didn't read about those regulations? Do you think that what they are worried about concerning battery safety SOMEHOW doesn't apply to you?? A battery fire IS a battery fire whether it occurs on a 747 or on a GP-15.
> >
> > The chemistry of the batteries involved on fires on ships, planes and cars are IDENTICAL to what you will be flying with in your GP-15. I am astounded by your denial of the very real safety risks concerning these batteries. I am, truly, at a loss for words...
> >
> > Tom
> I think you should learn the certification requirements for gliders, learn what the glider
> manufacturers are doing to meet these regulations, examine the problems electric gliders
> have had, and discuss the issues with as many knowledgeable people as you can. Only then
> will you have the knowledge needed to give us credible advice.
> --
> Eric Greenwell - USA
> - "A Guide to Self-launching Sailplane Operation"
> https://sites.google.com/site/motorgliders/publications

Of course I HAVE been presenting "problems electric gliders have had," but you discount each and every one of them, claiming that those problems have been solved or minimized. All of those gliders are still being flown. These problems will get worse as electric gliders age since battery failure mechanisms are age related. It is very interesting that the EASA electric aircraft certification standard was developed as a collaboration between EASA and Pipistrel, one of the manufacturers that you discount and the producer of one of the electric glider fatalities:
https://www.easa.europa.eu/light/topics/easas-type-certification-fully-electric-aircraft

Note that the EASA certification process for electric aircraft is still in its embryonic stages, and will change with time. I located the EASA applicable documents:
https://www.easa.europa.eu/light/topics/electric-sailplanes
One pertinent document on this page (https://www.easa.europa.eu/downloads/16912/en) contains the following disclaimer:

"EASA Position

The proposed use of Li-Batteries has prompted EASA to review the adequacy of the existing
battery requirements with respect to that chemistry. Lithium-Ion (Li-Ion) / Lithium Polymer (LiPo) Batteries, have specific failure and operational characteristics that could affect safety of
those battery installations and cause hazards to safety. On the other hand it is understood that
the characteristics of existing propulsion systems have contributed to quite a number of
accidents and electric propulsion systems with a simple and reliable start procedure can improve
safety significantly.

A safety assessment according (CS 2x.1309) is not required for Sailplanes and Powered
Sailplanes. The engine control units for these kind of aircraft are normally not qualified according
relevant EUROCAE/DO standards. Thus it is difficult to demonstrate that potentially hazardous
or catastrophic failures are improbable. It also cannot be expected that the effect of a thermal
runaway of Li batteries could be contained without any effect on the structural integrity of a
powered sailplane, but with good engineering judgement all potentially critical items should be
addressed to reduce the risk.

As the result of this review, EASA has determined that the amended special condition as
attached does adequately address installations of electric propulsion units and Li-Batteries and
due to the positive effect of reliable and simple electric propulsion units improves overall safety.
Additional requirements and notes introduced in this SC should help to identify relevant failure
modes and operational characteristics that have to be addressed with good engineering judgment
and necessary tests and qualification."

This is INCREDIBLE: EASA is basically saying "fly electric gliders at YOUR OWN RISK as we cannot certify their safety!" Another EASA Special Condition document does not specify any standards for the battery system but refers you to relevant safety standards such as RTCA DO 311 (https://www.easa.europa.eu/downloads/16912/en). These aren't free, but you are welcome to buy them yourself (https://www.docuwebs.org/61467-RTCA-DO-311.html).

On Tuesday, April 12, 2022 at 4:49:55 PM UTC-5, 2G wrote:
> On Tuesday, April 12, 2022 at 7:35:34 AM UTC-7, Eric Greenwell wrote:
> > On 4/11/2022 7:57 PM, 2G wrote:
> > > On Monday, April 11, 2022 at 3:42:41 PM UTC-7, Eric Greenwell wrote:
> > >> On 4/11/2022 2:57 PM, 2G wrote:
> > >>> On Monday, April 11, 2022 at 11:11:06 AM UTC-7, Eric Greenwell wrote:
> > >>>> On 4/10/2022 6:22 PM, 2G wrote:
> > >> ...
> > >>>>>
> > >>>>> To state there is little to no vibration in flight just isn't believable. Certainly, there is in any turbulent flight. Just entering and exiting a thermal is turbulent. Plus, the glider is exposed to substantial vibration during trailering and ground operations. And lithium battery thermal runaways have occurred in a vibration-free environment (i.e. battery farm fires). Plus, the batteries are being exposed to extreme altitude fluctuations, which subject them to atmospheric pressure stresses. While we still don't know the cause of the Felicity Ace fire, there were rough seas prior to its start.
> > >>>>>
> > >>>>> Tom
> > >>>> I haven't heard anyone speak of vibration while a glider is flying, unless the motor was
> > >>>> running. To clarify what I mean by vibration, I'll use an automobile analogy: vibration is
> > >>>> what you feel when driving on a washboarded road. Turbulence in glider is felt as G
> > >>>> loading, not vibration. In cars, an analog to glider turbulence is speed bumps and strong
> > >>>> wind gusts.
> > >>>>
> > >>>> I do agree that trailering effects on batteries in the glider are likely similar to what
> > >>>> cars experience with their batteries. I skimmed three studies on "vibration testing" 18650
> > >>>> cells used in cars; typically, they found some degradation in electrical performance and
> > >>>> some mechanical damage (observable with CAT scanning or similar), but made no mention of
> > >>>> fires. The strength, duration, the directions of test accelerations, and the chemistries
> > >>>> tested varied considerably between the studies I looked at.
> > >>>>
> > >>>> I have not seen anything about altitude pressure issues for 18650 cells, and I don't
> > >>>> expect an 8 psi ambient pressure reduction (sea level to FL180) to affect a 16850 cell
> > >>>> that can withstand much higher internal pressures. The effects I did read about are
> > >>>> reduced cooling due to thinner air, and reduced capacity due to lower temperatures.
> > >>>> --
> > >>>> Eric Greenwell - USA
> > >>>> - "A Guide to Self-launching Sailplane Operation"
> > >>>> https://sites.google.com/site/motorgliders/publications
> > >>>
> > >>> Eric,
> > >>>
> > >>> Flight safety is similar to guarding the President: the Secret Service has to be right 100% of the time, an assassin only has to be right once.. If we decide some factor is irrelevant and are wrong, then accidents can occur. The 737Max comes to mind.
> > >>>
> > >>> Did you read "Evaluation of Batteries for Safe Air Transport" (https://www.mdpi.com/1996-1073/9/5/340)? Section 4.2, Thermal and Mechanical Stress Testing, covers altitude pressure tests for batteries to be shipped by air. The situation is that if the battery case is sealed at sea level, and there is any air inside, it can create stress on the case when exposed to high altitudes. A manufacturer not listing a spec doesn't mean that spec is irrelevant ("absence of proof is not proof of absence").
> > >>>
> > >>> I can't understand why electric glider batteries shouldn't be subjected to the same tests required for shipment by air transport. Note that these regulations were developed following several major air disasters involving lithium batteries:
> > >>>
> > >> I did not read about air transport regulations, because gliders are not transporting
> > >> batteries, and the regulations for commercial carriage are hugely different EASA
> > >> regulations for gliders. The altitude tests you refer to are for the case, not for the
> > >> batteries.
> > >>
> > >> Seriously, Tom: fires in cars, fires in utility scale power banks, fires in ships carrying
> > >> thousands of cars, regulations for shipping batteries in commercial aircraft? These are
> > >> very tenuously related to what Schleicher, et al, are trying to do. They must follow the
> > >> regulations for our aircraft, and not for these other uses. Please spend most of your
> > >> effort on systems for gliders, their regulations, and how they are working out for soaring
> > >> pilots, and we will be better informed about the gliders we want to fly.
> > >> --
> > >> Eric Greenwell - USA
> > >> - "A Guide to Self-launching Sailplane Operation"
> > >> https://sites.google.com/site/motorgliders/publications
> > >
> > > WHY didn't read about those regulations? Do you think that what they are worried about concerning battery safety SOMEHOW doesn't apply to you?? A battery fire IS a battery fire whether it occurs on a 747 or on a GP-15.
> > >
> > > The chemistry of the batteries involved on fires on ships, planes and cars are IDENTICAL to what you will be flying with in your GP-15. I am astounded by your denial of the very real safety risks concerning these batteries. I am, truly, at a loss for words...
> > >
> > > Tom
> > I think you should learn the certification requirements for gliders, learn what the glider
> > manufacturers are doing to meet these regulations, examine the problems electric gliders
> > have had, and discuss the issues with as many knowledgeable people as you can. Only then
> > will you have the knowledge needed to give us credible advice.
> > --
> > Eric Greenwell - USA
> > - "A Guide to Self-launching Sailplane Operation"
> > https://sites.google.com/site/motorgliders/publications
> Of course I HAVE been presenting "problems electric gliders have had," but you discount each and every one of them, claiming that those problems have been solved or minimized. All of those gliders are still being flown. These problems will get worse as electric gliders age since battery failure mechanisms are age related. It is very interesting that the EASA electric aircraft certification standard was developed as a collaboration between EASA and Pipistrel, one of the manufacturers that you discount and the producer of one of the electric glider fatalities:
> https://www.easa.europa.eu/light/topics/easas-type-certification-fully-electric-aircraft
>
> Note that the EASA certification process for electric aircraft is still in its embryonic stages, and will change with time. I located the EASA applicable documents:
> https://www.easa.europa.eu/light/topics/electric-sailplanes
> One pertinent document on this page (https://www.easa.europa.eu/downloads/16912/en) contains the following disclaimer:
>
> "EASA Position
>
> The proposed use of Li-Batteries has prompted EASA to review the adequacy of the existing
> battery requirements with respect to that chemistry. Lithium-Ion (Li-Ion) / Lithium Polymer (LiPo) Batteries, have specific failure and operational characteristics that could affect safety of
> those battery installations and cause hazards to safety. On the other hand it is understood that
> the characteristics of existing propulsion systems have contributed to quite a number of
> accidents and electric propulsion systems with a simple and reliable start procedure can improve
> safety significantly.
>
> A safety assessment according (CS 2x.1309) is not required for Sailplanes and Powered
> Sailplanes. The engine control units for these kind of aircraft are normally not qualified according
> relevant EUROCAE/DO standards. Thus it is difficult to demonstrate that potentially hazardous
> or catastrophic failures are improbable. It also cannot be expected that the effect of a thermal
> runaway of Li batteries could be contained without any effect on the structural integrity of a
> powered sailplane, but with good engineering judgement all potentially critical items should be
> addressed to reduce the risk.
>
> As the result of this review, EASA has determined that the amended special condition as
> attached does adequately address installations of electric propulsion units and Li-Batteries and
> due to the positive effect of reliable and simple electric propulsion units improves overall safety.
> Additional requirements and notes introduced in this SC should help to identify relevant failure
> modes and operational characteristics that have to be addressed with good engineering judgment
> and necessary tests and qualification."
>
> This is INCREDIBLE: EASA is basically saying "fly electric gliders at YOUR OWN RISK as we cannot certify their safety!" Another EASA Special Condition document does not specify any standards for the battery system but refers you to relevant safety standards such as RTCA DO 311 (https://www.easa.europa.eu/downloads/16912/en). These aren't free, but you are welcome to buy them yourself (https://www.docuwebs.org/61467-RTCA-DO-311.html).
>
> And you can also confirm whether or not the GP-15 that you are going to receive is EASA certified (I don't think it will be because it is not a GP-15+).
>
> Tom

On Tuesday, April 12, 2022 at 3:11:17 PM UTC-7, phlyi...@gmail.com wrote:
> On Tuesday, April 12, 2022 at 4:49:55 PM UTC-5, 2G wrote:
> > On Tuesday, April 12, 2022 at 7:35:34 AM UTC-7, Eric Greenwell wrote:
> > > On 4/11/2022 7:57 PM, 2G wrote:
> > > > On Monday, April 11, 2022 at 3:42:41 PM UTC-7, Eric Greenwell wrote:
> > > >> On 4/11/2022 2:57 PM, 2G wrote:
> > > >>> On Monday, April 11, 2022 at 11:11:06 AM UTC-7, Eric Greenwell wrote:
> > > >>>> On 4/10/2022 6:22 PM, 2G wrote:
> > > >> ...
> > > >>>>>
> > > >>>>> To state there is little to no vibration in flight just isn't believable. Certainly, there is in any turbulent flight. Just entering and exiting a thermal is turbulent. Plus, the glider is exposed to substantial vibration during trailering and ground operations. And lithium battery thermal runaways have occurred in a vibration-free environment (i.e. battery farm fires). Plus, the batteries are being exposed to extreme altitude fluctuations, which subject them to atmospheric pressure stresses. While we still don't know the cause of the Felicity Ace fire, there were rough seas prior to its start.
> > > >>>>>
> > > >>>>> Tom
> > > >>>> I haven't heard anyone speak of vibration while a glider is flying, unless the motor was
> > > >>>> running. To clarify what I mean by vibration, I'll use an automobile analogy: vibration is
> > > >>>> what you feel when driving on a washboarded road. Turbulence in glider is felt as G
> > > >>>> loading, not vibration. In cars, an analog to glider turbulence is speed bumps and strong
> > > >>>> wind gusts.
> > > >>>>
> > > >>>> I do agree that trailering effects on batteries in the glider are likely similar to what
> > > >>>> cars experience with their batteries. I skimmed three studies on "vibration testing" 18650
> > > >>>> cells used in cars; typically, they found some degradation in electrical performance and
> > > >>>> some mechanical damage (observable with CAT scanning or similar), but made no mention of
> > > >>>> fires. The strength, duration, the directions of test accelerations, and the chemistries
> > > >>>> tested varied considerably between the studies I looked at.
> > > >>>>
> > > >>>> I have not seen anything about altitude pressure issues for 18650 cells, and I don't
> > > >>>> expect an 8 psi ambient pressure reduction (sea level to FL180) to affect a 16850 cell
> > > >>>> that can withstand much higher internal pressures. The effects I did read about are
> > > >>>> reduced cooling due to thinner air, and reduced capacity due to lower temperatures.
> > > >>>> --
> > > >>>> Eric Greenwell - USA
> > > >>>> - "A Guide to Self-launching Sailplane Operation"
> > > >>>> https://sites.google.com/site/motorgliders/publications
> > > >>>
> > > >>> Eric,
> > > >>>
> > > >>> Flight safety is similar to guarding the President: the Secret Service has to be right 100% of the time, an assassin only has to be right once. If we decide some factor is irrelevant and are wrong, then accidents can occur. The 737Max comes to mind.
> > > >>>
> > > >>> Did you read "Evaluation of Batteries for Safe Air Transport" (https://www.mdpi.com/1996-1073/9/5/340)? Section 4.2, Thermal and Mechanical Stress Testing, covers altitude pressure tests for batteries to be shipped by air. The situation is that if the battery case is sealed at sea level, and there is any air inside, it can create stress on the case when exposed to high altitudes. A manufacturer not listing a spec doesn't mean that spec is irrelevant ("absence of proof is not proof of absence").
> > > >>>
> > > >>> I can't understand why electric glider batteries shouldn't be subjected to the same tests required for shipment by air transport. Note that these regulations were developed following several major air disasters involving lithium batteries:
> > > >>>
> > > >> I did not read about air transport regulations, because gliders are not transporting
> > > >> batteries, and the regulations for commercial carriage are hugely different EASA
> > > >> regulations for gliders. The altitude tests you refer to are for the case, not for the
> > > >> batteries.
> > > >>
> > > >> Seriously, Tom: fires in cars, fires in utility scale power banks, fires in ships carrying
> > > >> thousands of cars, regulations for shipping batteries in commercial aircraft? These are
> > > >> very tenuously related to what Schleicher, et al, are trying to do.. They must follow the
> > > >> regulations for our aircraft, and not for these other uses. Please spend most of your
> > > >> effort on systems for gliders, their regulations, and how they are working out for soaring
> > > >> pilots, and we will be better informed about the gliders we want to fly.
> > > >> --
> > > >> Eric Greenwell - USA
> > > >> - "A Guide to Self-launching Sailplane Operation"
> > > >> https://sites.google.com/site/motorgliders/publications
> > > >
> > > > WHY didn't read about those regulations? Do you think that what they are worried about concerning battery safety SOMEHOW doesn't apply to you?? A battery fire IS a battery fire whether it occurs on a 747 or on a GP-15..
> > > >
> > > > The chemistry of the batteries involved on fires on ships, planes and cars are IDENTICAL to what you will be flying with in your GP-15. I am astounded by your denial of the very real safety risks concerning these batteries. I am, truly, at a loss for words...
> > > >
> > > > Tom
> > > I think you should learn the certification requirements for gliders, learn what the glider
> > > manufacturers are doing to meet these regulations, examine the problems electric gliders
> > > have had, and discuss the issues with as many knowledgeable people as you can. Only then
> > > will you have the knowledge needed to give us credible advice.
> > > --
> > > Eric Greenwell - USA
> > > - "A Guide to Self-launching Sailplane Operation"
> > > https://sites.google.com/site/motorgliders/publications
> > Of course I HAVE been presenting "problems electric gliders have had," but you discount each and every one of them, claiming that those problems have been solved or minimized. All of those gliders are still being flown. These problems will get worse as electric gliders age since battery failure mechanisms are age related. It is very interesting that the EASA electric aircraft certification standard was developed as a collaboration between EASA and Pipistrel, one of the manufacturers that you discount and the producer of one of the electric glider fatalities:
> > https://www.easa.europa.eu/light/topics/easas-type-certification-fully-electric-aircraft
> >
> > Note that the EASA certification process for electric aircraft is still in its embryonic stages, and will change with time. I located the EASA applicable documents:
> > https://www.easa.europa.eu/light/topics/electric-sailplanes
> > One pertinent document on this page (https://www.easa.europa.eu/downloads/16912/en) contains the following disclaimer:
> >
> > "EASA Position
> >
> > The proposed use of Li-Batteries has prompted EASA to review the adequacy of the existing
> > battery requirements with respect to that chemistry. Lithium-Ion (Li-Ion) / Lithium Polymer (LiPo) Batteries, have specific failure and operational characteristics that could affect safety of
> > those battery installations and cause hazards to safety. On the other hand it is understood that
> > the characteristics of existing propulsion systems have contributed to quite a number of
> > accidents and electric propulsion systems with a simple and reliable start procedure can improve
> > safety significantly.
> >
> > A safety assessment according (CS 2x.1309) is not required for Sailplanes and Powered
> > Sailplanes. The engine control units for these kind of aircraft are normally not qualified according
> > relevant EUROCAE/DO standards. Thus it is difficult to demonstrate that potentially hazardous
> > or catastrophic failures are improbable. It also cannot be expected that the effect of a thermal
> > runaway of Li batteries could be contained without any effect on the structural integrity of a
> > powered sailplane, but with good engineering judgement all potentially critical items should be
> > addressed to reduce the risk.
> >
> > As the result of this review, EASA has determined that the amended special condition as
> > attached does adequately address installations of electric propulsion units and Li-Batteries and
> > due to the positive effect of reliable and simple electric propulsion units improves overall safety.
> > Additional requirements and notes introduced in this SC should help to identify relevant failure
> > modes and operational characteristics that have to be addressed with good engineering judgment
> > and necessary tests and qualification."
> >
> > This is INCREDIBLE: EASA is basically saying "fly electric gliders at YOUR OWN RISK as we cannot certify their safety!" Another EASA Special Condition document does not specify any standards for the battery system but refers you to relevant safety standards such as RTCA DO 311 (https://www.easa.europa.eu/downloads/16912/en). These aren't free, but you are welcome to buy them yourself (https://www.docuwebs.org/61467-RTCA-DO-311.html).
> >
> > And you can also confirm whether or not the GP-15 that you are going to receive is EASA certified (I don't think it will be because it is not a GP-15+).
> >
> > Tom
> What ever happened to "I am truly at a loss for words...."

On 4/12/2022 2:49 PM, 2G wrote:
> On Tuesday, April 12, 2022 at 7:35:34 AM UTC-7, Eric Greenwell wrote:
>> On 4/11/2022 7:57 PM, 2G wrote:
>>> On Monday, April 11, 2022 at 3:42:41 PM UTC-7, Eric Greenwell wrote:
>>>> On 4/11/2022 2:57 PM, 2G wrote:
>>>>> On Monday, April 11, 2022 at 11:11:06 AM UTC-7, Eric Greenwell wrote:
>>>>>> On 4/10/2022 6:22 PM, 2G wrote:
>>>> ...
>>>>>>>
>>>>>>> To state there is little to no vibration in flight just isn't believable. Certainly, there is in any turbulent flight. Just entering and exiting a thermal is turbulent. Plus, the glider is exposed to substantial vibration during trailering and ground operations. And lithium battery thermal runaways have occurred in a vibration-free environment (i.e. battery farm fires). Plus, the batteries are being exposed to extreme altitude fluctuations, which subject them to atmospheric pressure stresses. While we still don't know the cause of the Felicity Ace fire, there were rough seas prior to its start.
>>>>>>>
>>>>>>> Tom
>>>>>> I haven't heard anyone speak of vibration while a glider is flying, unless the motor was
>>>>>> running. To clarify what I mean by vibration, I'll use an automobile analogy: vibration is
>>>>>> what you feel when driving on a washboarded road. Turbulence in glider is felt as G
>>>>>> loading, not vibration. In cars, an analog to glider turbulence is speed bumps and strong
>>>>>> wind gusts.
>>>>>>
>>>>>> I do agree that trailering effects on batteries in the glider are likely similar to what
>>>>>> cars experience with their batteries. I skimmed three studies on "vibration testing" 18650
>>>>>> cells used in cars; typically, they found some degradation in electrical performance and
>>>>>> some mechanical damage (observable with CAT scanning or similar), but made no mention of
>>>>>> fires. The strength, duration, the directions of test accelerations, and the chemistries
>>>>>> tested varied considerably between the studies I looked at.
>>>>>>
>>>>>> I have not seen anything about altitude pressure issues for 18650 cells, and I don't
>>>>>> expect an 8 psi ambient pressure reduction (sea level to FL180) to affect a 16850 cell
>>>>>> that can withstand much higher internal pressures. The effects I did read about are
>>>>>> reduced cooling due to thinner air, and reduced capacity due to lower temperatures.
>>>>>> --
>>>>>> Eric Greenwell - USA
>>>>>> - "A Guide to Self-launching Sailplane Operation"
>>>>>> https://sites.google.com/site/motorgliders/publications
>>>>>
>>>>> Eric,
>>>>>
>>>>> Flight safety is similar to guarding the President: the Secret Service has to be right 100% of the time, an assassin only has to be right once. If we decide some factor is irrelevant and are wrong, then accidents can occur. The 737Max comes to mind.
>>>>>
>>>>> Did you read "Evaluation of Batteries for Safe Air Transport" (https://www.mdpi.com/1996-1073/9/5/340)? Section 4.2, Thermal and Mechanical Stress Testing, covers altitude pressure tests for batteries to be shipped by air. The situation is that if the battery case is sealed at sea level, and there is any air inside, it can create stress on the case when exposed to high altitudes. A manufacturer not listing a spec doesn't mean that spec is irrelevant ("absence of proof is not proof of absence").
>>>>>
>>>>> I can't understand why electric glider batteries shouldn't be subjected to the same tests required for shipment by air transport. Note that these regulations were developed following several major air disasters involving lithium batteries:
>>>>>
>>>> I did not read about air transport regulations, because gliders are not transporting
>>>> batteries, and the regulations for commercial carriage are hugely different EASA
>>>> regulations for gliders. The altitude tests you refer to are for the case, not for the
>>>> batteries.
>>>>
>>>> Seriously, Tom: fires in cars, fires in utility scale power banks, fires in ships carrying
>>>> thousands of cars, regulations for shipping batteries in commercial aircraft? These are
>>>> very tenuously related to what Schleicher, et al, are trying to do. They must follow the
>>>> regulations for our aircraft, and not for these other uses. Please spend most of your
>>>> effort on systems for gliders, their regulations, and how they are working out for soaring
>>>> pilots, and we will be better informed about the gliders we want to fly.
>>>> --
>>>> Eric Greenwell - USA
>>>> - "A Guide to Self-launching Sailplane Operation"
>>>> https://sites.google.com/site/motorgliders/publications
>>>
>>> WHY didn't read about those regulations? Do you think that what they are worried about concerning battery safety SOMEHOW doesn't apply to you?? A battery fire IS a battery fire whether it occurs on a 747 or on a GP-15.
>>>
>>> The chemistry of the batteries involved on fires on ships, planes and cars are IDENTICAL to what you will be flying with in your GP-15. I am astounded by your denial of the very real safety risks concerning these batteries. I am, truly, at a loss for words...
>>>
>>> Tom
>> I think you should learn the certification requirements for gliders, learn what the glider
>> manufacturers are doing to meet these regulations, examine the problems electric gliders
>> have had, and discuss the issues with as many knowledgeable people as you can. Only then
>> will you have the knowledge needed to give us credible advice.
>> --
>> Eric Greenwell - USA
>> - "A Guide to Self-launching Sailplane Operation"
>> https://sites.google.com/site/motorgliders/publications
>
> Of course I HAVE been presenting "problems electric gliders have had," but you discount each and every one of them, claiming that those problems have been solved or minimized. All of those gliders are still being flown. These problems will get worse as electric gliders age since battery failure mechanisms are age related. It is very interesting that the EASA electric aircraft certification standard was developed as a collaboration between EASA and Pipistrel, one of the manufacturers that you discount and the producer of one of the electric glider fatalities:
> https://www.easa.europa.eu/light/topics/easas-type-certification-fully-electric-aircraft
>
> Note that the EASA certification process for electric aircraft is still in its embryonic stages, and will change with time. I located the EASA applicable documents:
> https://www.easa.europa.eu/light/topics/electric-sailplanes
> One pertinent document on this page (https://www.easa.europa.eu/downloads/16912/en) contains the following disclaimer:
>
> "EASA Position
>
> The proposed use of Li-Batteries has prompted EASA to review the adequacy of the existing
> battery requirements with respect to that chemistry. Lithium-Ion (Li-Ion) / Lithium Polymer (LiPo) Batteries, have specific failure and operational characteristics that could affect safety of
> those battery installations and cause hazards to safety. On the other hand it is understood that
> the characteristics of existing propulsion systems have contributed to quite a number of
> accidents and electric propulsion systems with a simple and reliable start procedure can improve
> safety significantly.
>
> A safety assessment according (CS 2x.1309) is not required for Sailplanes and Powered
> Sailplanes. The engine control units for these kind of aircraft are normally not qualified according
> relevant EUROCAE/DO standards. Thus it is difficult to demonstrate that potentially hazardous
> or catastrophic failures are improbable. It also cannot be expected that the effect of a thermal
> runaway of Li batteries could be contained without any effect on the structural integrity of a
> powered sailplane, but with good engineering judgement all potentially critical items should be
> addressed to reduce the risk.
>
> As the result of this review, EASA has determined that the amended special condition as
> attached does adequately address installations of electric propulsion units and Li-Batteries and
> due to the positive effect of reliable and simple electric propulsion units improves overall safety.
> Additional requirements and notes introduced in this SC should help to identify relevant failure
> modes and operational characteristics that have to be addressed with good engineering judgment
> and necessary tests and qualification."
>
> This is INCREDIBLE: EASA is basically saying "fly electric gliders at YOUR OWN RISK as we cannot certify their safety!" Another EASA Special Condition document does not specify any standards for the battery system but refers you to relevant safety standards such as RTCA DO 311 (https://www.easa.europa.eu/downloads/16912/en). These aren't free, but you are welcome to buy them yourself (https://www.docuwebs.org/61467-RTCA-DO-311.html).
>
> And you can also confirm whether or not the GP-15 that you are going to receive is EASA certified (I don't think it will be because it is not a GP-15+).
>
> Tom
>
THe most interesting remark in your posting was this: "On the other hand it is understood
that the characteristics of existing propulsion systems have contributed to quite a number
of accidents and electric propulsion systems with a simple and reliable start procedure
can improve safety significantly."

On Tuesday, April 12, 2022 at 8:22:48 PM UTC-7, Eric Greenwell wrote:
> On 4/12/2022 2:49 PM, 2G wrote:
> > On Tuesday, April 12, 2022 at 7:35:34 AM UTC-7, Eric Greenwell wrote:
> >> On 4/11/2022 7:57 PM, 2G wrote:
> >>> On Monday, April 11, 2022 at 3:42:41 PM UTC-7, Eric Greenwell wrote:
> >>>> On 4/11/2022 2:57 PM, 2G wrote:
> >>>>> On Monday, April 11, 2022 at 11:11:06 AM UTC-7, Eric Greenwell wrote:
> >>>>>> On 4/10/2022 6:22 PM, 2G wrote:
> >>>> ...
> >>>>>>>
> >>>>>>> To state there is little to no vibration in flight just isn't believable. Certainly, there is in any turbulent flight. Just entering and exiting a thermal is turbulent. Plus, the glider is exposed to substantial vibration during trailering and ground operations. And lithium battery thermal runaways have occurred in a vibration-free environment (i.e. battery farm fires). Plus, the batteries are being exposed to extreme altitude fluctuations, which subject them to atmospheric pressure stresses. While we still don't know the cause of the Felicity Ace fire, there were rough seas prior to its start.
> >>>>>>>
> >>>>>>> Tom
> >>>>>> I haven't heard anyone speak of vibration while a glider is flying, unless the motor was
> >>>>>> running. To clarify what I mean by vibration, I'll use an automobile analogy: vibration is
> >>>>>> what you feel when driving on a washboarded road. Turbulence in glider is felt as G
> >>>>>> loading, not vibration. In cars, an analog to glider turbulence is speed bumps and strong
> >>>>>> wind gusts.
> >>>>>>
> >>>>>> I do agree that trailering effects on batteries in the glider are likely similar to what
> >>>>>> cars experience with their batteries. I skimmed three studies on "vibration testing" 18650
> >>>>>> cells used in cars; typically, they found some degradation in electrical performance and
> >>>>>> some mechanical damage (observable with CAT scanning or similar), but made no mention of
> >>>>>> fires. The strength, duration, the directions of test accelerations, and the chemistries
> >>>>>> tested varied considerably between the studies I looked at.
> >>>>>>
> >>>>>> I have not seen anything about altitude pressure issues for 18650 cells, and I don't
> >>>>>> expect an 8 psi ambient pressure reduction (sea level to FL180) to affect a 16850 cell
> >>>>>> that can withstand much higher internal pressures. The effects I did read about are
> >>>>>> reduced cooling due to thinner air, and reduced capacity due to lower temperatures.
> >>>>>> --
> >>>>>> Eric Greenwell - USA
> >>>>>> - "A Guide to Self-launching Sailplane Operation"
> >>>>>> https://sites.google.com/site/motorgliders/publications
> >>>>>
> >>>>> Eric,
> >>>>>
> >>>>> Flight safety is similar to guarding the President: the Secret Service has to be right 100% of the time, an assassin only has to be right once.. If we decide some factor is irrelevant and are wrong, then accidents can occur. The 737Max comes to mind.
> >>>>>
> >>>>> Did you read "Evaluation of Batteries for Safe Air Transport" (https://www.mdpi.com/1996-1073/9/5/340)? Section 4.2, Thermal and Mechanical Stress Testing, covers altitude pressure tests for batteries to be shipped by air. The situation is that if the battery case is sealed at sea level, and there is any air inside, it can create stress on the case when exposed to high altitudes. A manufacturer not listing a spec doesn't mean that spec is irrelevant ("absence of proof is not proof of absence").
> >>>>>
> >>>>> I can't understand why electric glider batteries shouldn't be subjected to the same tests required for shipment by air transport. Note that these regulations were developed following several major air disasters involving lithium batteries:
> >>>>>
> >>>> I did not read about air transport regulations, because gliders are not transporting
> >>>> batteries, and the regulations for commercial carriage are hugely different EASA
> >>>> regulations for gliders. The altitude tests you refer to are for the case, not for the
> >>>> batteries.
> >>>>
> >>>> Seriously, Tom: fires in cars, fires in utility scale power banks, fires in ships carrying
> >>>> thousands of cars, regulations for shipping batteries in commercial aircraft? These are
> >>>> very tenuously related to what Schleicher, et al, are trying to do. They must follow the
> >>>> regulations for our aircraft, and not for these other uses. Please spend most of your
> >>>> effort on systems for gliders, their regulations, and how they are working out for soaring
> >>>> pilots, and we will be better informed about the gliders we want to fly.
> >>>> --
> >>>> Eric Greenwell - USA
> >>>> - "A Guide to Self-launching Sailplane Operation"
> >>>> https://sites.google.com/site/motorgliders/publications
> >>>
> >>> WHY didn't read about those regulations? Do you think that what they are worried about concerning battery safety SOMEHOW doesn't apply to you?? A battery fire IS a battery fire whether it occurs on a 747 or on a GP-15.
> >>>
> >>> The chemistry of the batteries involved on fires on ships, planes and cars are IDENTICAL to what you will be flying with in your GP-15. I am astounded by your denial of the very real safety risks concerning these batteries. I am, truly, at a loss for words...
> >>>
> >>> Tom
> >> I think you should learn the certification requirements for gliders, learn what the glider
> >> manufacturers are doing to meet these regulations, examine the problems electric gliders
> >> have had, and discuss the issues with as many knowledgeable people as you can. Only then
> >> will you have the knowledge needed to give us credible advice.
> >> --
> >> Eric Greenwell - USA
> >> - "A Guide to Self-launching Sailplane Operation"
> >> https://sites.google.com/site/motorgliders/publications
> >
> > Of course I HAVE been presenting "problems electric gliders have had," but you discount each and every one of them, claiming that those problems have been solved or minimized. All of those gliders are still being flown. These problems will get worse as electric gliders age since battery failure mechanisms are age related. It is very interesting that the EASA electric aircraft certification standard was developed as a collaboration between EASA and Pipistrel, one of the manufacturers that you discount and the producer of one of the electric glider fatalities:
> > https://www.easa.europa.eu/light/topics/easas-type-certification-fully-electric-aircraft
> >
> > Note that the EASA certification process for electric aircraft is still in its embryonic stages, and will change with time. I located the EASA applicable documents:
> > https://www.easa.europa.eu/light/topics/electric-sailplanes
> > One pertinent document on this page (https://www.easa.europa.eu/downloads/16912/en) contains the following disclaimer:
> >
> > "EASA Position
> >
> > The proposed use of Li-Batteries has prompted EASA to review the adequacy of the existing
> > battery requirements with respect to that chemistry. Lithium-Ion (Li-Ion) / Lithium Polymer (LiPo) Batteries, have specific failure and operational characteristics that could affect safety of
> > those battery installations and cause hazards to safety. On the other hand it is understood that
> > the characteristics of existing propulsion systems have contributed to quite a number of
> > accidents and electric propulsion systems with a simple and reliable start procedure can improve
> > safety significantly.
> >
> > A safety assessment according (CS 2x.1309) is not required for Sailplanes and Powered
> > Sailplanes. The engine control units for these kind of aircraft are normally not qualified according
> > relevant EUROCAE/DO standards. Thus it is difficult to demonstrate that potentially hazardous
> > or catastrophic failures are improbable. It also cannot be expected that the effect of a thermal
> > runaway of Li batteries could be contained without any effect on the structural integrity of a
> > powered sailplane, but with good engineering judgement all potentially critical items should be
> > addressed to reduce the risk.
> >
> > As the result of this review, EASA has determined that the amended special condition as
> > attached does adequately address installations of electric propulsion units and Li-Batteries and
> > due to the positive effect of reliable and simple electric propulsion units improves overall safety.
> > Additional requirements and notes introduced in this SC should help to identify relevant failure
> > modes and operational characteristics that have to be addressed with good engineering judgment
> > and necessary tests and qualification."
> >
> > This is INCREDIBLE: EASA is basically saying "fly electric gliders at YOUR OWN RISK as we cannot certify their safety!" Another EASA Special Condition document does not specify any standards for the battery system but refers you to relevant safety standards such as RTCA DO 311 (https://www.easa.europa.eu/downloads/16912/en). These aren't free, but you are welcome to buy them yourself (https://www.docuwebs.org/61467-RTCA-DO-311.html).
> >
> > And you can also confirm whether or not the GP-15 that you are going to receive is EASA certified (I don't think it will be because it is not a GP-15+).
> >
> > Tom
> >
> THe most interesting remark in your posting was this: "On the other hand it is understood
> that the characteristics of existing propulsion systems have contributed to quite a number
> of accidents and electric propulsion systems with a simple and reliable start procedure
> can improve safety significantly."
> Until you understand the current situation, you will be unable to understand why electric
> gliders are so attractive, and ineffective in persuading people that they are too
> dangerous. The major reason is the promise of increased safety of operation over gas
> powered gliders; secondly, the reduction in maintenance. Most of us understand
> electrification will introduce some risks different from gas powered gliders, but we think
> the tradeoff will result in increased safety and more enjoyable soaring. No one is
> requiring you to follow us into the future, you've made your point repeatedly, so, please,
> relax and enjoy your glider, and let us enjoy the gliders we choose.
> --
> Eric Greenwell - USA
> - "A Guide to Self-launching Sailplane Operation"
> https://sites.google.com/site/motorgliders/publications